This invention relates to a polymer sheet having a surface fabric veil layer masked by a surface polymer film layer; and a method of heating such a laminate.
Thermoplastic laminates comprising a polymer and a reinforcement means are known in the art. Such known laminates and methods of their preparation are disclosed in many patents and publications. Examples of reinforced thermoplastic laminates are disclosed in U.S. Pat. Nos.: 4,302,269; 4,291,084; 4,269,884; 4,255,219; 4,238,266; 4,240,857; 4,098,943; 4,044,188; 3,745,140; 3,833,453; 3,765,998; 3,850,723; 3,318,757; 3,531,369. These patents are a nonlimiting illustration of the state of the art of reinforced thermoplastic laminates and are incorporated by reference.
Thermoplastic reinforced laminates known in the art are either shaped into articles of manufacture immediately upon being laminated, or are put into some blank form. The thermoplastic laminate blank is later reheated and formed into the desired shape. A problem which has been encountered during the reheating of thermoplastic blanks is that the thermoplastic material becomes soft and sticky. The surface adheres to supporting means in the means to heat the laminate blank causing the laminate blank to deform while being removed from the supporting means. One solution to this problem is to place a thin fiberglass fabric veil on the surface of the laminate. This veil is located between the laminate and the laminate support in the heating means. The thin fiber glass veil can be laminated to the surface of the laminate during lamination. U.S. Pat No. 4,238,266 discloses the use of a surface fiberglass veil layer and its advantages. This veil prevents the heated laminate from adhering to the laminate support surface. Such laminate support surfaces are usually oven shelves, or conveyor belt surfaces either solid or foraminous. The difficulty in removing the heated laminate results not only in a disruption of the laminate surface where it adheres to the laminate support but also results in distortion of the laminate as the laminate is attempted to be removed from the laminate support. Additionally the surface veil prevents the laminate from sagging after it has been heated. The use of this type of veil is generally detrimental to smooth surface appearance and results in the veil being only partially impregnated into the surface of the laminate. Not only is the surface appearance somewhat deteriorated, but when the veil is made of glass it results in a scratchy surface with exposed fiberglass which easily breaks off and is difficult to handle.
It is known in the art to use surface mats such as those disclosed in U.S. Pat. Nos. 3,850,723; 3,713,962 and 3,664,909. The use of an embedded surface layer is also disclosed in GB No. 1341438 and Canadian Pat. No. 837,044. When a light weight fabric such as that disclosed in Great Britain Pat. No. 1341438 is embedded in the surface, a small amount of the fibers protrude and can cause scratching of the skin during handling. Canadian Pat. No. 837,044 discloses a laminate containing a fabric reinforcing layer having a thin outer thermoplastic sheet. However, Canadian Pat. No. 837,044 does not disclose the use of a surface thermoplastic layer with a thin fabric veil which permits preheating the laminate without the laminate adhering to the laminate support of the heating means.
It is known in the art to use thin surface layers of polymeric material to improve the surface appearance of laminates. This is particularly illustrated in GB No. 1547280.